I have just started using CROCO and have a few general questions regarding mixing parameterization. When the GLS sub-grid turbulence model is used (e.g., define GLS_MIXING), do the variables Akv_Bak and Akt_Bak in croco.in specify values of background viscosity and diffusivity or should they be set to zeros?
Also, I notice that there is a GLS_MIXING_3D option that is recommended for NBQ simulations in the tutorial. I would like to know if the ‘3D’ label means the turbulence model yields turbulence parameters in both vertical and horizontal directions.
Akv_Bak and Akt_Bak are not active when using GLS_MIXING. This code has its own background parameters in gls_mixing.F if you want to do modifications.
You are correct about GLS_MIXING_3D. 3D means turbulent viscosity/diffusivity is set for both vertical and horizontal directions. It also means that all shear components are computed to provide a source of TKE, not just du/dz.
Many thanks for your quick reply. I suppose when GLS_MIXING_3D is used, I should also set those lateral mixing parameters in croco.in to zeros, since GLS_MIXING_3D covers all directions.
The value of lateral viscosity/diffusivity in croco.in will be added to the total
Thanks again. I will note this down.